In spite of careful planning and proper attention to the appropriate precautions, launch vehicles occasionally stray from their desired flight path. Often this errant behavior, although undesirable, poses no danger to the general population. However, in some cases the errant path leads off the test range toward populated areas. Thus, it may become necessary to destroy a launch vehicle in flight to prevent it from reaching a populated area. Launch vehicles which are capable of receiving and acting upon a command to "self-destruct" are widely known in the art.
However, those of skill in the art recognize that self-destruction may be directed toward different goals. At a minimum, self-destruction has the goal of rendering the launch vehicle non-propulsive. A more ambitious goal is to somehow prevent the non-propulsive launch vehicle from reaching populated areas.
The conventional means used to render a rocket motor non-propulsive depends in part on whether the rocket motor is powered by liquid fuel or by solid fuel. In vehicles that are propelled by one or more liquid fuel rocket motors, the liquid fuel is transported from storage tanks through pipes to a combustion chamber. The pipes include valves for controlling the flow of fuel. Such a launch vehicle can therefore be rendered non-propulsive by simply closing the valves to shut off the supply of fuel. Without fuel supplied to the combustion chamber, the currently ignited stage will cease combustion and become non-propulsive. Ensuring closure of the appropriate valves will likewise render non-propulsive all as yet unignited liquid fuel stages of a multi-stage liquid fuel rocket motor.
Unfortunately, it is generally not possible to render a solid fuel rocket motor non-propulsive by shutting off the fuel supply. In a solid fuel rocket motor the solid fuel is typically formed into a cylindrical or bottle-shaped mass that surrounds and substantially defines the combustion chamber. Thus, there is no valve separating the fuel supply from the combustion chamber such that closing the valve will shut off the fuel supply. Once a mass of solid fuel is ignited, it typically burns continuously until substantially all of the fuel is consumed.
In order to render an ignited solid fuel rocket motor stage non-propulsive, it is therefore conventional to fracture the case with an explosive charge. The case is typically fractured by exploding a linear shaped charge that is positioned adjacent the motor case. The fractured case is unable to resist the combustion pressures created by the operating motor. As a result, a crack is created in the case and the propellant. Combustion products then travel through the crack to the ambient environment instead of taking the normal path through the rocket motor's nozzle. As a result, the combustion chamber loses pressure and the ignited stage is rendered non-propulsive.
Nothing need be done to unignited solid fuel stages to render them non-propulsive; unless their propellant is ignited, they will remain non-propulsive. However, as a precaution against inadvertent ignition, the case of each unignited upper stage in a multi-stage solid fuel launch vehicle is generally fractured when the launch vehicle is ordered to self-destruct. An explosive charge is typically exploded against each unignited stage's motor case to fracture each case sufficiently to prevent normal pressurization of the motor.
The force of the explosion often does not fracture the propellant within the case sufficiently to create a crack that connects the combustion chamber with the ambient environment. Instead, the explosion merely weakens a region of the case by fracturing that case region, and weakens the adjacent region of the propellant by denying that propellant region the structural support that would be provided by an intact case. Thus, if an upper stage is inadvertently ignited during the self-destruction, the weakened regions of the case and propellant will give way, a crack will open, and the stage will be rendered non-propulsive because it is unable to pressurize normally.
If the launch vehicle is sufficiently far from populated areas when the self-destruct command is received and the currently ignited motor is rendered non-propulsive, the vehicle will fall out of flight before it poses any danger to the populace. However, on rare occasions the launch vehicle may have already attained sufficient height and momentum to reach a populated area even though the vehicle is no longer being propelled by a rocket motor. Simply rendering the vehicle non-propulsive is not sufficient if the vehicle is close enough for non-propulsive, but substantially intact, stages to reach the populated area. Impact of the launch vehicle or parts thereof in the populated area may cause extensive damage, injuries, or even fatalities.
A major concern is the size of the non-propulsive launch vehicle parts. When fractured or cracked by conventional destruction systems, the upper stages of multi-stage solid fuel rocket motors typically remain in substantially one piece. Indeed, several fractured but substantially intact stages may remain secured to one another after "destruction" of the launch vehicle. Many ballistic missiles and new generation launch vehicles include at least two solid fuel stages, with a single stage sometimes weighing well over 100,000 pounds. Thus, even if a multi-stage solid fuel rocket motor is split into separate stages, and even if the ignited stage is rendered non-propulsive, and even if the cases of the unignited upper stages are fractured, conventional approaches may still allow extremely large pieces of explosive debris to fall upon a populated area.
Thus, it would be an advancement in the art to provide a system and method for shattering a previously unignited solid fuel rocket motor into many smaller pieces.
It would also be an advancement to provide a system and method which assist in shattering a launch vehicle that is attached to the solid fuel rocket motor.
Such a system and method are disclosed and claimed herein.